Three places where people know your name before you have anything to announce.
Indie Hackers, Discord and Slack communities pay off only if you were there before you needed them. Thirty days of showing up is the price of admission.
Judge a Discord by messages per day in its main channels. A server with 20,000 members and forty messages a week is empty.
Answer questions in your area of competence. This is the whole mechanism; there is no shortcut version of it.
Even pre-launch you know something specific. Post the thing you learned this week, not an introduction thread.
Three communities you are genuinely present in beat fifteen you lurk in. Presence is the asset.